Vehicle air supply systems include an air dryer that receives air from a compressor and supplies air to supply reservoirs for vehicle operating systems. The air dryer includes materials that remove moisture and particulates from the air prior to supplying the air to the supply reservoirs. The supply reservoirs supply air to vehicle operating systems such as suspension and brake systems. Clean, dry air is needed to reduce component wear and to maintain system operating efficiencies.
In one known configuration, the air dryer includes a desiccant material that removes moisture from air supplied by the compressor. During a compression cycle, air flows through the desiccant material to the supply reservoirs until a desired pressure level is achieved. Once the desired pressure level is achieved, the compressor is unloaded. During unloading, the desiccant material is regenerated by purging. Air held within a purge reservoir is used to regenerate the desiccant material.
Traditionally, the purge reservoir is internally formed within the air dryer. However, some vehicle air supply systems require a separate purge reservoir. To accommodate these systems, a separate tank is installed on a vehicle to provide the separate purge reservoir. One disadvantage with using a separate tank is that in addition to another tank, additional fluid connections are required, both of which increase assembly time and cost. Further, the separate tank and additional fluid connections increase weight, which adversely affects fuel economy.
Another disadvantage is that the separate tank is mounted to a vehicle frame member, which takes up packaging space that would otherwise be useful for other vehicle systems. Further, various mounting configurations and/or hardware are required to attach the separate tank to different vehicle frame configurations. This proliferates parts, increases cost, and increases assembly time.
Thus, there is a need for a vehicle air supply system that includes a separate purge reservoir for an air dryer, but which does not require a separate tank.